abnormal shifting on 1995 Dodge Intrepid

My transmission will shift into reverse fine and it will shift into the first and second gears fine but that is as high as it will shift. Anything past the second gear the engine will just wind out and it won't shift. Could this be a vaccum line or a modulator valve or does my model Intrepid even have either. I have a 1995 Dodge inhtrepid.

Asked by for the 1995 Dodge Intrepid
It sounds like there is no third gear or higher in your Dodge.
Best to scan the Transmission, to see what codes are in there, it sounds like it could be a shift solenoid that is not working which replaced all the vacuum modulators that you mentioned.
Your car has it's own Transmission Control Module that does in fact have self-diagnostic ability. I would use it, that is why it is there.
Thank you, that was a helpful answer but I was wondering how I go about checking that out? Do I need to have it hooked up to a diagnostic or does it have a computer under the dash that I can use a computer key on?